Instrument for describing arcs of circles.



A. w. ALLEN. INSTRUMENT FOB DESCRIBING ARCS 0F OIRGLES. I APPLICATION FIIQIJD SEPT.24. 1908.

Patented Mar. 23, 1909.

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UNITED srarns rn'rnnr err-ion.

.\LONZQ w; ALLEN, or s'ranirroit; lL'L INOIS, ASSIGNOR F ONE-HALF TO JAMES F. LrNon: or STREATQR, ILLINOIS.

INSTRUMENT FOR DE SCRIBI'NG ARCS OF CIRCLES Application filed September the use of'a central oint; and it consists in the peculiar and a vantageous instrument hereinafter described and particularly pointed out in the claims appended.

In the drawings, accompanying and forming part of this specification: Figurel is a plan view illustrating the three members of my novel instrument as the same appear when properly arranged in the firstinstance relative to a cord line from which the arc of a circle is to be drawn, and also showing by dotted lines the adjustment of the markercarrying bar of the major member that is re-. sorted to when it is desired to'draw a line enlarged vertical section taken through the maj or member of the instrument in the plane indicated by the line 22 of Fig. 1. Fig. 3. is a section taken through one of the auxiliary members of the instrument in the plane indicated by the line 3-3 of Fig. 1. Fig. 4 is a detail cross-section on line 4-4'of Fig. 1. Fig. 5 is detail side elevation of the forward portion of the marker-carryingbar.

Similar letters designate corresponding parts in all of the views of the drawings, referring to which:

A is the major member of my improved instrument, and B B are the auxiliary menihers; the said auxiliary members being formed of steel-or other suitable material and being each providedwith a point a and with two (more or.le ss) depending barbs b. The major member A comprises a longitudinally terminates at its forward end in an upwardly extending portion .e on which is a vertically disposed sleeve having opposite notches g; and'in the said s eevefis a vertically-movable parallel to the arc of the circle. Fig. 2 is an slotted bar 0, and two arms d d The bar 0' lunger h which has opposite studs i disposed I Specification of. Letters Patent. Patented. March 23, 1909.

24, 1908. Serial No. 454,577.

the plunger his reduced and threaded, as indicated by m, for the engagement of a tubular cap 1) and inclosed in-the said cap and interposed between the top of the same and the upper end of the sleeve f is a coiled spring 1- which has for its oflice to yieldingly support the cap 22 and the plunger h in the position shown in Fig. 3. Thus it will be seen that the marker in theholder lc- (winch marker may be a pencil, as shown, a pen or the like) is nor- .mally maintained above the surface on which the instrument is placed, and yet by siinily pressing downwardly on the cap 1) the marker may be carried into contact with said sur- 1" will operate to raise the cap 1), the plunger h and the marker-holder 7c, and will then yieldingly maintain saidparts in their raised position as before described;

The arm d of the major. member A is pro- .vided at its inner end with an enlargement s in which is a slot-t and on which is a protractor 'w, subdivided into degrees. The arm (1 of said member A is provided at its inner end with an enlargement 1), having a slot to and a pointer a; the latter to cooperate with the before mentioned protractor u. Said arm d is also provided at its underside with a rib y, Fig. 4, the office of which is to bear on the surface on which the instrument is placed with a view of supporting the arm (Z in ahorizontal plane parallel to that of the are pivotally connected together in the manthe medium of a pin having a head a, disposed under the arm a, and also having a circular shank portion 1) disposed in said arm 61, and an angular shank portion 0 dis posed in an angular aperture (1 in the arm 01- and further having a threaded socket e, a washer f arranged above the armtd and below the marker-carrying bar and having an angular aperture receiving" the angular shank ortion c of-the pin, and a screw having a and g which bears on the markercarrying bar, and also having a threaded shank h disposed in the threaded socket e of the pin. Thus it will be seen that when the screw is loosened the marker carrying bar may be adjusted in the direction of its adjustably-fixed together through the meface. When, however, the cap p is relieved of pressure, it will be observed that the spring ner shown in Fig. 2-that is to saythrough length on the shankhf. The arms cl d are lower surface of .arm d. The arms (I and (1. s

I 'complished by adjusting the d (1 respectively, and

dium ofa pin having a head is disposed under the arme and an angular shank portion Z disposed in the slots t and w of the arms also having a threaded socket m, a washer a arranged on the arm (i and under the marker-carrying bar, and a screw having a portion 0 arranged in the slot of the marker-carrying bar, and a threaded shank '1) extending into the threaded socket 172 of the pin and also having a head 1', larger in diameter than the portion 0, disposed above the marker-carrying bar. The portion 0 of the screw isoi a diameter to bear against the upper side of the washer n and enable the screw to clamp the arms (1 d between the washera and the pin head is disposed under the arm (Z. Thus it will be seen-that when the arms 61 d are adjustably fixed together, and it is desired to adjust the marker-carrying bar horizontally, it is not necessary to loosen the screw having shank p and head 1*; the space between the washer n and the screw head 1", when the arms cl ol' are clamped between washer a and head is, being, of course) sufficient for the free horie zontal movement of the marker-carrying bar. On the other hand it ie simply necessary to loosen thescrew having the head 9 when the marker-carrying bar may be expeditiously and easily moved forward or backward and may then be adjustably fixed with respect to the arms d at by simply tightening the screw having the head 9.

In the practical use'of the instrument, the auxiliary members B are, by the embedding of their barbs b in the paper or other surface on which the are is to be described, fixed in position with their points located at the ends of the cord line, indicated by M, and after the armed d of the major member A are ad'- justed to the required, degree- 5. e.,to determine the radiusof the arcthe said arms at (Z are placed against the,points of the members B, Fig. 1, and are moved against said points after the mannershown in Fig. 1

to move the marker, which is of course at such. time depressed, from one end to the other of the cord line M and thereby describe the arc.- After the arc is described, if it is desired to. make one or more lines parallel with the arc these-me maybe readily acmarker-carrymg bar forward! and then. manipulating the major member d as before.

The construction herein illustrated and described const'itutes'the best practical embodiment of my hivefition of which I am cognizant, but it is obvibus that in the future practice of the invention such chan es or modiiifcations'may be made as fairly fal within the scope of my invention as deiin'ed in the claims appended.

Having described my invention, what I claim and desire to secure by Letters-latent,1s:

1. An instrument for the purpose described, comprising means for affording hearing points at the ends of a cord line, and a member comprising arms pivotally connected together and adapted to be arranged and moved against the said bearing points, a

marker, and a marker-carrying barconnect-' ed and movable with the arms and adjustable lengthwisc thereonto carry the marker toward and from the said pivotal connection ,between the arms.

2'. An instrument [or the purpose dc- ,scribed, comprising means for affording hearing points at the ends of a cord line, a member comprising arms adapted to be arranged. and moved against the bee ring points, means pivotally connecting said arms together, means for adi'ustably fixing the arms with respect to eac 1 other, marking means, and a bar carrying said marking means and engaged with and adpistablc with respect to said means pivotal y connecting the arms together and said means for adj ustabl y fixing the arms with respect to each other.

3. An instrument for the purpose described, comprising means for affording hearing points at the ends of a cord line, and a .member comprising arms pivotally connected'together by means including a set screw and adapted to be arranged and moved against said bearing points; one of said members having a protractor and the other having a pointer, means for ad'ustablfy fixing the arms with respect to each other, and a slotted bar carrying a marker and engaged by the means for adjustably fixing the arms with respect to each other and adapted to he adj ustably fixed by the said set screw.

'4. In an instrument for the purpose -described, the combination of a vertically disposed sleeve, a plunger movable endwise and heldag'ainst turning in the sleeve and adcpted to carry marking means, a tubular cap secured on the olunger and movable on the sleeve, and a ooi ed spring inclosed in the cap and inter )osed between the upper end sleeve am the top of the cap.

In testimony whereof I have hereunto set my hand in presence of two subscribing wi(. nesses.

AlJONZO W. ALLEN.

Witnesses PAUL MENrN-erm, THos. F. HENRY.

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